Hello PlantedMan!

I can tell you're a big fan of The Simpsons! You knew where to find all those quotes and sound bites from the show! I especially enjoyed the one about blaming Apu.

It looks like you were trying out some green screen effects with the background in front of the Kwik-E-Mart. I've done a bit of green screening myself, and I've found one of the "key" aspects is to have a larger distance between your subject and the green screen itself. It reduces the amount of green that reflects onto your subject that you are keying.
Another factor is the evenness of lighting on the green screen. If you have folds in the fabric or any variance of light and dark green, it means you have to tell the software to remove a larger color range from your video, which increases the likelihood that something you don't want to disappear will be wiped out.
One last thing that you can do to improve color-keying with Lego is to find a way to give your Lego pieces a matte finish. If you're brave enough, you can spray hairspray on them to reduce the amount of green that will reflect. This is useful SPECIFICALLY when you have a large flat surface that is reflecting a LOT of green from the background.

All-in-All a worthy addition to your brickfilmography!
-Nate Swihart